The present invention relates to a multistage spin type substrate processing system for applying a photoresist onto a substrate such as a semiconductor wafer and for developing the same.
In a photolithographic process for manufacturing a semiconductor device, a photoresist is applied onto a surface of a semiconductor wafer, and is pattern-exposed and developed. For such a series of substrate processes, for example, a substrate processing system disclosed in U.S. Pat. No. 5,664,254 is used.
As shown in FIGS. 1 and 2, a conventional substrate processing system 100 comprises a cassette station 110 having a first subarm mechanism 21, process sections 111, 112 and 113, each having a main arm mechanism 24, and an interface section 114 having a second subarm mechanism 26. As shown in FIG. 1, the main arm mechanism 24 is provided on the center of each of the first, second and third process sections 111, 112 and 113, and various processing device groups G1 to G15 are provided to surround the main arm mechanism 24 on all sides. Liquid treatment system processing device groups G1 to G6 are provided on the front side of the processing system 100, and heat treatment system processing device groups G7 to G15 are provided on the back side and the side face side of the processing system 100.
As shown in FIG. 2, each of the liquid treatment system processing device groups G1 to G6 comprise pairs of right and left units BCTs, COTs and DEVs stacked vertically in two stages. A spin rotation liquid treating device having a cup CP and a spin chuck SC is provided in each of the units BCT, COT and DEV. In order to prevent a contamination from being caused by sticking of particles and the like and to stabilize process performance during a liquid treatment, clean air having a temperature and a humidity controlled is introduced into each of the units BCT, COT and DEV, and air is forcibly discharged from each of the units BCT, COT and DEV.
In such a processing system 100, a wafer W is fetched from a cassette CR of the cassette station 110 by the first subarm mechanism 21 and is transferred to the main arm mechanism 24, a treating solution for a substrate reflection preventing film is applied onto the wafer W by the applying unit BCT in the first process section 111 and is baked, the resist solution is applied onto the wafer W by the applying unit COT provided in the second process section 112 and is baked, and the wafer W is further transferred to the second subarm mechanism 26, is delivered to an exposure system (not shown) through the interface section 114 and is subjected to an exposing treatment. Furthermore, the wafer W is delivered into the third process section 113 through the interface section 114, is baked (PEB) after the exposure, is subjected to a developing treatment by the developing unit DEV, and is rinsed, dried and finally returned to the cassette CR of the cassette station 110.
With an increase in the size of the wafer, a user has greatly desired an increase in the process number (a high throughput) per unit time in order to further enhance productivity. In a series of resist processes, however, the fineness of a circuit pattern has further been enhanced and the wafer size has further been increased and a time taken for each process step tends to be increased. Therefore, it has been hard to enhance the throughput. In order to obtain a clear pattern at a developing step, for example, it is also necessary to keep a developing time as long as possible. In a chemical amplification type photoresist, particularly, the same wafer W is repeatedly subjected to the developing process twice or three times in order to enhance a resolution during the development. For this reason, a long time is required for the process so that the throughput is easily lowered.
In step of applying and forming a reflection preventing film and a photoresist film on a wafer by a spin applying method, it is necessary to reduce a wafer rotating speed in order to achieve film thickness uniformity with an increase in a wafer diameter from 8 inches to 12 inches. Consequently, it takes too much time to shake a resist solution off and to perform a drying process. Consequently, the throughput tends to be reduced.
If another process section is further provided on the conventional substrate processing system 100 to enhance the throughput of the substrate process, the footprint (occupied floor space) of the device is increased. When the footprint of the device is increased, the total floor space of a clean room is necessarily increased, and an equipment investment and a running cost for controlling a clean room environment are excessively increased. For this reason, the user has greatly desired that the footprint of the device should be reduced as much as possible.
Furthermore, it is regulated that a distance between the floor of the clean room and a ceiling thereof should be equal to or smaller than 3.5 m. Therefore, it is necessary to make the height of the whole system smaller than an upper limit (3.5 m) of the height of the clean room. Within a range meeting the room height limiting conditions, the stacked conventional spin units have a limit of two stages. In order to further enhance the throughput of the resist applying and developing processes, a consumer has greatly desired that the spin units can be stacked in three stages or more.
It is an object of the present invention to provide a multistage spin type substrate processing system which has a high throughput and a small footprint and meets the height limiting conditions of a clean room.
The present invention provides a multistage spin type substrate processing system comprising a multistage spin unit having a plurality of compartments stacked vertically in a multistage, a main arm mechanism comprising a holder for holding a processed substrate to put the processed substrate in and out of each of the compartments, and driving means for causing the holder to advance and retreat longitudinally, moving the holder up and down along a vertical shaft and turning the holder around the vertical shaft, a spin chuck provided on each of the compartments for holding and spin-rotating the substrate delivered by the main arm mechanism, a cup for surrounding the spin chuck to receive and discharge a treatment solution separated from the substrate by centrifugal force, a common nozzle for supplying the treatment solution toward the substrate held by the spin chuck in the compartment, a nozzle moving passageway provided along the multistage spin unit for communicating with the compartment to move the common nozzle therethrough, and a nozzle moving mechanism for moving the common nozzle.
The system according to the present invention aggregates more liquid treating devices having a spin rotating method into one multistage spin unit than that in the prior art. Therefore, the throughput of the liquid treatment can be enhanced. Furthermore, one nozzle is shared, or in common with, the liquid treating devices. Therefore, the size of each of the liquid treating devices is reduced. Consequently, the size of the device is reduced as a whole (particularly, the height of the device is reduced) and the footprint of the device in a clean room is further reduced. Furthermore, the spin rotating liquid treating section, the main arm mechanism section and heat treating section can be modularized respectively, and each of them can be divided into blocks to be delivered and assembled. Therefore, the device can be delivered into and installed in the clean room more easily than in the prior art. Furthermore, a multistage spin processing system device group (multistage spin unit) is arranged in a vertical line differently from the prior art in which it is arranged in two horizontal lines. Consequently, the main delivery arm mechanism and the multistage spin processing system device group arranged in a vertical one line can be caused to correspond to each other at a ratio of 1 to 1. In addition, a shift between the center of the main delivery arm mechanism and the cup center of the multistage spin processing system device group (multistage spin unit) is reduced so that the cup can be provided on the center of the compartment. Consequently, accessories can be provided symmetrically on the right and left in the cup so that the unit can be shared on the right and left.
In this case, it is preferred that the multistage spin unit should have compartments which are stacked vertically in at least two stages or more and the same process treating section such as a resist applying section, a treating section, a resist developing section or the like should be provided in each compartment. Thus, a liquid can be supplied to a plurality of treating sections by means of the same nozzle. Furthermore, since the same chemicals treatment is performed by the multistage spin unit, other chemicals atmosphere is not mixed so that safety can be kept.
Furthermore, it is preferred that a rinse nozzle for supplying a rinse solution to the substrate should be provided in the compartment. For example, in the case where the rinse nozzle is shared, excessive development and uneven development (defective development uniformity) are caused if a rinse starting timing is delayed after the development. Therefore, it is desirable that the rinse nozzle should be provided in each compartment. However, it is also possible to share one rinse nozzle between a plurality of developing devices for a liquid treatment which makes no troubles for the timing.
Moreover, it is preferred that the system should further comprise a clean air introducing mechanism provided in an upper portion of the compartment for introducing clean air having a temperature and humidity regulated every compartment, a dividing member having an opening formed for putting the common nozzle in and out and serving to divide the nozzle moving passageway from the compartment, and an exhaust mechanism for exhausting the nozzle moving passageway. Thus, the clean air is introduced downward into each compartment, flows into the nozzle moving passageway through the opening of the dividing member, that is, the access opening of the common nozzle, goes down in the nozzle moving passageway and is discharged downward. In this case, the nozzle moving passageway is divided from each compartment by the dividing member. Therefore, the air always flows from the opening to the moving passageway, and particles generated in the nozzle moving mechanism do not enter the compartment but can be efficiently discharged together with a downward flow of the clean air.
Furthermore, it is preferable that the system should further comprise a collecting drain device communicating with each of the cups through a drain passageway, and a collecting exhaust device communicating with the cup through an exhaust passageway. By discharging liquid and air from the cup belonging to the same multistage spin unit toward the collecting drain device and the collecting exhaust device, the piping structure of a drainage and exhaust system can be simplified so that the discharged substances can be managed all together. For this reason, it is desirable that the same chemicals treatment should be carried out in one multistage spin processing system device group (multistage spin unit).
Furthermore, it is preferred that the system should further comprise an opening/closing valve provided on the exhaust passageway and a controller for controlling an operation of the opening/closing valve in such a manner that exhaust timings of the cups do not overlap each other. Thus, a large number of cups are controllably exhausted so that a maximum instantaneous displacement is reduced and a load applied to the collecting exhaust device on the plant side can be relieved. In addition, an exhaust flow rate in the multistage spin processing system device group (multistage spin units) can be always kept constant by the controller and a supplied air volume is constant. Therefore, a pressure balance on the inside can be kept at a constant positive pressure. Consequently, it is possible to prevent a contamination from entering from the outside.
With reference to FIGS. 3A to 3C, an exhaust timing of a conventional resist applying treatment will be described below. In a first applying unit COT1, the exhaust of a cup CP is started at a time T0. On the other hand, the exhaust of the cup CP is started at a time T11 in a second supplying unit COT2. The exhaust starting timing time T11 of the COT2 is later than the exhaust starting timing time T0 of the COT1 by a predetermined time. At this time, a displacement V11 of the cup CP is small and constant. In the first applying unit COT1, the displacement of the cup CP is then increased from V11 to V12 at a time T12 that a resist solution is started to be discharged from the nozzle toward the wafer W. At times T12 to T14, the resist is applied onto the wafer W while exhausting the cup CP with a large displacement V12. After the time T14 is passed, the displacement of the cup CP is returned from V12 to V11. On the other hand, in the second applying unit COT2, the displacement of the cup CP is increased from V11 to V12 at the time T13 that the resist solution is started to be discharged from the nozzle toward the wafer W. At the times T13 to T15, the resist is applied onto the wafer W while exhausting the cup CP with the large displacement V12. After the time T15 is passed, the displacement of the cup CP is returned from V12 to V11. As shown in FIG. 3C, an exhaust period from the time T12 to the time T14 and a period from the time T13 to the time T15 partially overlap each other. For this reason, a maximum displacement V15 in the cap CP sometimes exceeds an exhaust capacity (maximum capability) of the collecting exhaust device. Therefore, it is hard to rapidly discharge a mist of the resist solution from the inside of the cup CP.
With reference to FIGS. 4A to 4C, the exhaust timing of a conventional developing treatment will be described below. In a first developing unit DEV1, the cup CP is exhausted for a period from a time T0 to a time T22 and a period from a time T24 to a time T28, and the exhaust of the cup CP is stopped for a period from the time T22 to the time T24. On the other hand, in a second developing unit DEV2, the cup CP is exhausted for a period from a time T21 to a time T23 and a period from a time T26 to a time T29, and the exhaust of the cup CP is stopped for a period from the time T23 to the time T26. At this time, each displacement V21 of the cup CP is small and constant.
In the first developing unit DEV1, a developing solution is started to be discharged from the nozzle toward the wafer W at the time T0, the discharge of the developing solution is stopped at the time T22, and a latent image pattern in a resist film is developed with the developing solution put on the wafer W (in a liquid filling state) for a period from the time T22 to the time T24 (an exhaust stopping period). Then, the discharge of pure water from the nozzle is started at the time T24, the wafer W is rinsed, and the discharge of the pure water from the nozzle is stopped at the time T28. A period from the time T0 to the time T25 is an effective developing treatment period.
On the other hand, in the second developing unit DEV2, the developing solution is started to be discharged from the nozzle toward the wafer W at the time T21, the discharge of the developing solution is stopped at the time T23, and a latent image pattern in a resist film is developed with the developing solution put on the wafer W (in the liquid filling state) for a period from the time T23 to the time T26 (the exhaust stopping period). Then, the discharge of pure water from the nozzle is started at the time T26, the wafer W is rinsed, and the discharge of the pure water from the nozzle is stopped at the time T29. A period from the time T21 to the time T27 is an effective developing treatment period.
As shown in FIG. 4C, the period from the time T0 to the time T22 and the period from the time T21 to the time T23 partially overlap each other. Moreover, the period from the time T24 to the time T28 and the period from the time T26 to the time T29 partially overlap each other. For this reason, a maximum displacement V22 in the cap CP sometimes exceeds the exhaust capacity (maximum capability) of the collecting exhaust device. Therefore, it is hard to rapidly discharge a mist of the developing solution from the inside of the cup CP.
It is preferred that a thin motor having a smaller vertical thickness than in the prior art should be used for the spin chuck. Even if a spin unit (compartment) having four stages is stacked vertically by using the thin motor, the whole height of the system can fully achieve an upper limit (3.5 m) of the height of a clean room. However, the thickness of the cup cannot be reduced. The reason is that the function of discharging a mist-like process solution from the inside of the cup is deteriorated if the height (depth) of the cup is reduced (becomes small) excessively. For this reason, the height (depth) of the cup cannot be reduced (become small) unnecessarily.
It is preferred that the nozzle moving mechanism should comprise an elevator mechanism for moving the shared nozzle along the nozzle moving passageway, and a swinging and turning mechanism for swinging and turning the common nozzle around a vertical shift. When the common nozzle goes up and down along the nozzle moving passageway to reach the front face of a target compartment in the multistage spin unit, it swings and turns and is inserted into the compartment through an opening.
Furthermore, it is preferred that the system should comprise a heating unit having a hot plate provided apart from the multistage spin unit for heating the substrate, and a cooling unit provided below the heating unit for cooling the substrate. It is preferred that these heat treating units should be constituted in a multistage and should be set to another module separated from the multistage spin processing system device group (multistage spin unit) in consideration of thermal effect.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.